The blast was reported at 8:45 a.m. Wednesday at the home at 6716 Simpson Ave., according to the Los Angeles Fire Department.

“The explosion was significant enough to knock over a single block wall between that property and neighboring properties,” said firefighter David Ortiz, spokesman for the LAFD at the scene on Wednesday. “It also blew out windows of surrounding neighbors’ homes and a commercial building on Lankershim (Boulevard).”

Ortiz said when he went to the rear of the home where the explosion occurred, “you can smell marijuana.”

“There’s a lot of structural damage,” Ortiz said, adding he was not able to go through the entire building to check it out further. He explained that the LAFD arson unit and the LAPD were investigating.

“There’s no reason for us to hurry an investigation,” he said, adding that he could not give a timeline for the investigation.

A 24-year-old man was rushed to a hospital in critical condition with blast injuries. Two other men, ages 21 and 55, were treated at the scene and released, said department spokeswoman Margaret Stewart.

Neighbors, media and onlookers could be seen Wednesday at the property, which was surrounded by yellow fire department caution tape.

The home where the explosion occurred was surrounded by a gate that made it difficult to see the damage in the rear.

The back unit of the residence, where the explosion occurred, was red-tagged, while the front unit was yellow-tagged, Ortiz said. A red tag means entry is prohibited, while a yellow tag means residents can use part of the home.

A yellow tag was also placed on the unit south of the explosion site on the other side of the block wall, Ortiz said.

Manuel Gomez, 61, lives in an apartment on Archwood Street, not far from where the explosion happened.

“The explosion was so hard, it made the floor shake,” Gomez said as he walked down the street near the incident. “Everybody felt it because it was so hard.”

Raymond Signor, 58, was trying to sell video footage of the aftermath to local news outlets near the property. He said he lives a couple of houses down from the incident.

“There was a big electrical surge,” Signor said, which was not unusual for the neighborhood. “After that surge, like 2 minutes after that, it shook your whole body back and forth. It shook the whole house.”